Method and device for arp operation in communication system supporting multiple links

ABSTRACT

A method and a device are disclosed for address resolution protocol (ARP) operation in a communication system supporting multiple links. An operation method of a first device comprises the steps of: receiving, from a communication node, an ARP request packet requesting the transmission of a MAC address of a second device connected to the first device; finding, in an ARP table stored in the first device, a representative MAC address of the second device requested by the ARP request packet; and transmitting an ARP response packet including the representative MAC address to the communication node.

CROSS-REFERENCE TO RELATED APPLICATIONS

This application is a U.S. national stage of International ApplicationNo. PCT/KR2021/016359, filed on Nov. 10, 2021, which claims priority toKorean Patent Application No. 10-2020-0152082 filed on Nov. 13, 2020 andKorean Patent Application No. 10-2021-0154003 filed on Nov. 10, 2021,the entire disclosures of each of which are incorporated herein byreference.

TECHNICAL FIELD

The present disclosure relates to a wireless local area network (LAN)communication technique, and more particularly, to a technique fortransmitting and receiving Internet protocol (IP) packets based on aproxy address resolution protocol (ARP) in a communication systemsupporting multiple links.

BACKGROUND

Recently, as the spread of mobile devices expands, a wireless local areanetwork (LAN) technology capable of providing fast wirelesscommunication services to mobile devices is in the spotlight. Thewireless LAN technology may be a technology that supports mobiledevices, such as smart phones, smart pads, laptop computers, portablemultimedia players, embedded devices, and the like, to wirelessly accessthe Internet based on wireless communication technology.

The standards using the wireless LAN technology are being standardizedas IEEE802.11 standards mainly in the Institute of Electrical andElectronics Engineers (IEEE). As the above-described wireless LANtechnologies have been developed and spread, applications using thewireless LAN technologies have been diversified, and a demand for awireless LAN technology supporting a higher throughput has arisen.Accordingly, a frequency bandwidth (e.g., ‘maximum 160 MHz bandwidth’ or‘80+80 MHz bandwidth’) used in the IEEE 802.1 lac standard has beenexpanded, and the number of supported spatial streams has alsoincreased. The IEEE 802.11ac standard may be a very high throughput(VHT) wireless LAN technology supporting a high throughput of 1 gigabitper second (Gbps) or more. The IEEE 802.11ac standard can supportdownlink transmission for multiple stations by utilizing the MIMOtechniques.

As applications requiring higher throughput and applications requiringreal-time transmission occur, the IEEE 802.11be standard, which is anextreme high throughput (EHT) wireless LAN technology, is beingdeveloped. The goal of the IEEE 802.11be standard may be to support ahigh throughput of 30 Gbps. The IEEE 802.11be standard may supporttechniques for reducing a transmission latency. In addition, the IEEE802.11be standard can support a more expanded frequency bandwidth (e.g.,320 MHz bandwidth), multi-link transmission and aggregation operationsincluding multi-band operations, multiple access point (AP) transmissionoperations, and/or efficient retransmission operations (e.g., hybridautomatic repeat request (HARQ) operations).

However, since multi-link operations are operations not defined in theexisting wireless LAN standard, it may be necessary to define detailedoperations according to an environment in which the multi-linkoperations are performed. In particular, methods for supportinglow-power operations in the multi-link environment may be required.

Meanwhile, the technologies that are the background of the presentdisclosure are written to improve the understanding of the background ofthe present disclosure and may include content that is not already knownto those of ordinary skill in the art to which the present disclosurebelongs.

SUMMARY

The present disclosure is directed to providing a method and anapparatus for a proxy address resolution protocol (ARP) operation in acommunication system supporting multiple links.

Technical Solution

An operation method of a first device, according to a first embodimentof the present disclosure for achieving the above-described objective,may comprise receiving, from a communication node, an address resolutionprotocol (ARP) request packet requesting transmission of a medium accesscontrol (MAC) address of a second device associated with the firstdevice. The operation method may also comprise identifying arepresentative MAC address of the second device, which is requested bythe ARP request packet, from an ARP table stored in the first device.The operation method may also comprise transmitting, to thecommunication node, an ARP response packet including the representativeMAC address.

The first device may be an access point (AP) multi-link device (MLD).The second device may be a station (STA) MLD. The STA MLD may include aSTA1 and a STA2. A first MAC address of the STA MLD, a second MACaddress of the STA1, and a third MAC address of the STA2 may beconfigured independently of each other. The representative MAC addressmay be the first MAC address.

The ARP request packet may include an indicator requesting provision ofthe representative MAC address.

The operation method may further comprise receiving a data frame fromthe communication node. The operation method may further comprise inresponse to that a receiver address of the data frame is set to therepresentative MAC address of the second device, generating a firstphysical layer convergence protocol (PLCP) protocol data unit (PPDU) anda second PPDU based on data included in the data frame. The operationmethod may further comprise transmitting the first PPDU to a STA1included in the second device. The operation method may further comprisetransmitting the second PPDU to a STA2 included in the second device.

The operation method may further comprise determining a trafficidentifier (TID) based on a type of the data and identifying a firstlink and a second link mapped to the TID among multiple links. The firstPPDU is transmitted to the STA1 through the first link, and the secondPPDU is transmitted to the STA2 through the second link.

A size of a first data unit included in the first PPDU may be equal to asize of a second data unit included in the second PPDU, and the firstdata unit and the second data unit may be generated based on the data.

The first PPDU may include a first data unit generated based on thedata, the second PPDU may include a second data unit generated based onthe data, and a size of the first data unit and a size of the seconddata unit may be determined based on link occupancy states.

The ARP request packet may include an Internet protocol (IP) address ofthe second device, the ARP request packet may not be transmitted to thesecond device, and the ARP response packet may be transmitted by thefirst device on behalf of the second device.

The ARP table may include an IP address and a MAC address of the seconddevice associated with the first device and a MAC address of each of oneor more STAs included in the second device.

The ARP table may be generated based on information included in messagestransmitted and received in an IP address acquisition procedureperformed by the second device.

The first device may be an AP MLD, the second device may be a STA MLD,and the first device may be associated with the second device throughmultiple links.

A first device, according to a second embodiment of the presentdisclosure for achieving the above-described objective, may comprise: aprocessor and a memory storing one or more instructions executable bythe processor. The one or more instructions are executed to performreceiving, from a communication node, an address resolution protocol(ARP) request packet requesting transmission of a medium access control(MAC) address of a station 1 (STA1) included in a second deviceassociated with the first device. The one or more instructions are alsoexecuted to perform identifying a MAC address of the STA1, which isrequested by the ARP request packet, from an ARP table stored in thefirst device. The one or more instructions are also executed to performtransmitting, to the communication node, an ARP response packetincluding the MAC address of the STA1.

The ARP request packet may include an Internet protocol (IP) address ofthe STA1, the ARP request packet may not be transmitted to the seconddevice or the STA1, and the ARP response packet may be transmitted bythe first device on behalf of the second device or the STA1.

The second device may include one or more STAs, and an IP address ofeach of the second device and the one or more STAs may be configuredindependently.

The ARP table may include an IP address and a MAC address of the seconddevice associated with the first device and an IP address and a MACaddress of each of one or more STAs included in the second device.

The ARP table may be generated based on information included in messagestransmitted and received in an IP address acquisition procedureperformed by each of the second device and the one or more STAs.

The one or more instructions may be further executed to performreceiving a data frame from the communication node. The one or moreinstructions may be further executed to perform in response to that areceiver address of the data frame is set to the MAC address of the STA1included in the second device, generating a first physical layerconvergence protocol (PLCP) protocol data unit (PPDU) based on dataincluded in the data frame. The one or more instructions may be furtherexecuted to perform transmitting the first PPDU to the second device. Anaddress 1 field included in the first PPDU is set to a MAC address ofthe STA MLD, an address 2 field included in the first PPDU is set to aMAC address of the AP MLD, an address field 3 included in the first PPDUis set to the MAC address of the STA1, and an address 4 field includedin the first PPDU is set to a MAC address of the communication node.

According to the present disclosure, an access point (AP) multi-linkdevice (MLD) may store an address resolution protocol (ARP) tableincluding an Internet protocol (IP) address and a medium access control(MAC) address of a station (STA) MLD and transmit an ARP response packetbased on the ARP table on behalf of the STA MLD. Accordingly,unnecessary ARP operations by communication nodes other than the AP MLDcan be prevented, radio resources can be efficiently used, and ARPoperations can be performed quickly.

BRIEF DESCRIPTION OF DRAWINGS

FIG. 1 is a block diagram illustrating a first embodiment of acommunication node constituting a wireless local area network (LAN)system.

FIG. 2 is a conceptual diagram illustrating a first embodiment ofmulti-links configured between multi-link devices (MLDs).

FIG. 3 is a sequence chart illustrating a first embodiment of anegotiation procedure for a multi-link operation in a wireless LANsystem.

FIG. 4 is a sequence chart illustrating a first embodiment of a methodfor transmitting and receiving data according to an address resolutionprotocol (ARP) operation in a wireless LAN system.

FIG. 5A is a block diagram illustrating a first embodiment of a formatof an ARP packet.

FIG. 5B is a block diagram illustrating a first embodiment of anEthernet frame.

FIG. 6 is a sequence chart illustrating a second embodiment of a methodfor transmitting and receiving data according to an ARP operation in awireless LAN system.

FIGS. 7A and 7B are sequence charts illustrating a third embodiment of amethod for transmitting and receiving data according to an ARP operationin a wireless LAN system.

FIG. 8 is a block diagram illustrating a first embodiment of an MPDU.

DETAILED DESCRIPTION

Since the present disclosure may be variously modified and have severalforms, specific embodiments are shown in the accompanying drawings andare described in the detailed description. It should be understood,however, that it is not intended to limit the present disclosure to thespecific embodiments but. On the contrary, the present disclosure isintended to cover all modifications and alternatives falling within thespirit and scope of the present disclosure.

Relational terms, such as first, second, and the like, may be used fordescribing various elements, but the elements should not be limited bythe terms. These terms are only used to distinguish one element fromanother. For example, a first component may be named as a secondcomponent without departing from the scope of the present disclosure,and the second component may also be similarly named as the firstcomponent. The term “and/or” means any one or a combination of aplurality of related and described items.

In embodiments of the present disclosure, “at least one of A and B” mayrefer to “at least one of A or B” or “at least one of combinations ofone or more of A and B”. In addition, “one or more of A and B” may referto “one or more of A or B” or “one or more of combinations of one ormore of A and B”.

When it is mentioned that a certain component is “coupled with” or“connected with” another component, it should be understood that thecertain component is directly “coupled with” or “connected with” to theother component or a further component may be disposed therebetween. Incontrast, when it is mentioned that a certain component is “directlycoupled with” or “directly connected with” another component, it shouldbe understood that a further component is not disposed therebetween.

The terms used in the present disclosure are only used to describespecific embodiments and are not intended to limit the presentdisclosure. The singular expression includes the plural expressionunless the context clearly dictates otherwise. In the presentdisclosure, terms such as ‘comprise’ or ‘have’ are intended to designatethat a feature, number, step, operation, component, part, or combinationthereof described in the specification exists. However, it should beunderstood that the terms do not preclude existence or addition of oneor more features, numbers, steps, operations, components, parts, orcombinations thereof.

Unless otherwise defined, all terms (including technical and scientificterms) used herein have the same meaning as commonly understood by oneof ordinary skill in the art to which this disclosure belongs. Termsthat are generally used and have been in dictionaries should beconstrued as having meanings consistent with contextual meanings in theart. In this description, unless defined clearly, terms are notnecessarily construed as having formal meanings.

Hereinafter, forms of the present disclosure are described in detailwith reference to the accompanying drawings. In describing thedisclosure, to facilitate the entire understanding of the disclosure,like numbers refer to like elements throughout the description of thefigures and the repetitive description thereof has been omitted.

In the following, a wireless communication system to which embodimentsaccording to the present disclosure are applied is described. Thewireless communication system to which the embodiments according to thepresent disclosure are applied is not limited to the contents describedbelow, and the embodiments according to the present disclosure can beapplied to various wireless communication systems. A wirelesscommunication system may be referred to as a ‘wireless communicationnetwork’.

FIG. 1 is a block diagram illustrating a first embodiment of acommunication node constituting a wireless local area network (LAN)system.

As shown in FIG. 1 , a communication node 100 may be an access point, astation, an access point (AP) multi-link device (MLD), or a non-AP MLD.The access point may refer to an AP, and the station may refer to a STAor a non-AP STA. The operating channel width supported by the accesspoint may be 20 megahertz (MHz), 80 MHz, 160 MHz, or the like. Theoperating channel width supported by the station may be 20 MHz, 80 MHz,or the like.

The communication node 100 may include at least one processor 110, amemory 120, and a plurality of transceivers 130 connected to a networkto perform communications. The transceiver 130 may be referred to as atransceiver, a radio frequency (RF) unit, an RF module, or the like. Inaddition, the communication node 100 may further include an inputinterface device 140, an output interface device 150, a storage device160, and the like. The components included in the communication node 100may be connected by a bus 170 to communicate with each other.

However, the respective components included in the communication node100 may be connected through individual interfaces or individual busescentering on the processor 110 instead of the common bus 170. Forexample, the processor 110 may be connected to at least one of thememory 120, the transceiver 130, the input interface device 140, theoutput interface device 150, or the storage device 160 through adedicated interface.

The processor 110 may execute at least one instruction stored in atleast one of the memory 120 or the storage device 160. The processor 110may refer to a central processing unit (CPU), a graphics processing unit(GPU), or a dedicated processor on which the methods according to theembodiments of the present disclosure are performed. Each of the memory120 and the storage device 160 may be configured as at least one of avolatile storage medium or a nonvolatile storage medium. For example,the memory 120 may be configured with at least one of a read only memory(ROM) or a random access memory (RAM).

FIG. 2 is a conceptual diagram illustrating a first embodiment ofmulti-links configured between MLDs.

As shown in FIG. 2 , an MLD may have one medium access control (MAC)address. In embodiments, the MLD may mean an AP MLD and/or a non-AP MLD.The MAC address of the MLD may be used in a multi-link setup procedurebetween the non-AP MLD and the AP MLD. The MAC address of the AP MLD maybe different from the MAC address of the non-AP MLD. AP(s) affiliatedwith the AP MLD may have different MAC addresses, and station(s)(STA(s)) affiliated with the non-AP MLD may have different MACaddresses. Each of the APs having different MAC addresses may be incharge of each link and may perform a role of an independent AP.

Each of the STAs having different MAC addresses may be in charge of eachlink and may perform a role of an independent STA. The non-AP MLD may bereferred to as a STA MLD. The MLD may support simultaneous transmit andreceive (STR) operations. In this case, the MLD may perform atransmission operation on a link 1 and may perform a reception operationon a link 2. The MLD supporting the STR operations may be referred to asan STR MLD (e.g., STR AP MLD, STR non-AP MLD). In embodiments, a linkmay refer to a channel or band. A device that does not support the STRoperations may be referred to as a non-simultaneous transmit and receive(NSTR) AP MLD or an NSTR non-AP MLD (or NSTR STA MLD).

A multi-link operation may include multi-band transmission. The AP MLDmay include a plurality of access points, and the plurality of accesspoints may operate on different links. Each of the plurality of accesspoints may perform function(s) of a lower MAC layer. Each of theplurality of access points may be referred to as a ‘communication node’or ‘lower entity’. The communication node (i.e., access point) mayoperate under controls of an upper layer (or the processor 110 shown inFIG. 1 ). The non-AP MLD may include a plurality of stations, and theplurality of stations may operate on different links. Each of theplurality of stations may be referred to as a ‘communication node’ or‘lower entity’. The communication node (i.e., station) may operate undercontrols of an upper layer (or the processor 110 shown in FIG. 1 ).

The MLD may perform communication in a multi-band. One frequency band(e.g., one channel) used by the MLD may be defined as one link.Alternatively, a plurality of links may be configured in one frequencyband used by the MLD. For example, the MLD may configure one link in the2.4 GHz band and two links in the 6 GHz band. The respective links maybe referred to as a first link, a second link, and a third link.Alternatively, the respective links may be referred to as a link 1, alink 2, and a link 3. A link number may be set by the AP, and anidentifier (ID) may be assigned to each link.

The MLD (e.g., AP MLD and/or non-AP MLD) may configure a multi-link byperforming an access procedure and/or a negotiation procedure for amulti-link operation. In this case, the number of links and/or link(s)to be used in the multi-link may be configured. The non-AP MLD (e.g.,station) may identify information on band(s) capable of communicatingwith the AP MLD. In the negotiation procedure for a multi-link operationbetween the non-AP MLD and the AP MLD, the non-AP MLD may configure oneor more links among links supported by the AP MLD to be used for themulti-link operation. A station that does not support a multi-linkoperation (e.g., IEEE 802.11a/b/g/n/ac/ax STA) may access one or morelinks of the multi-link supported by the AP MLD.

Each of the AP MLD and the STA MLD may have an MLD MAC address, and eachAP and STA operating on each link may have a MAC address. The MLD MACaddress of the AP MLD may be referred to as an ‘AP MLD MAC address’ or‘AP MLD address’, and the MLD MAC address of the STA MLD may be referredto as a ‘STA MLD MAC address’ or ‘non-AP MLD address’. The MAC addressof the AP may be referred to as an ‘AP MAC address’ or ‘AP address’, andthe MAC address of the STA may be referred to as a ‘STA MAC address’ or‘non-AP STA address’. In embodiments, the AP MLD MAC address may referto the AP MLD address, the STA MLD MAC address may refer to the non-APMLD address, the AP MAC address may refer to the AP address, and the STAMAC address may refer to the non-AP STA address. In a multi-linknegotiation procedure, the AP MLD MAC address and the STA MLD MACaddress may be used. The AP address and the STA address may be exchangedand/or configured in the multi-link negotiation procedure.

When the multi-link negotiation procedure is completed, the AP MLD maygenerate an address table and may manage and/or update the addresstable. One AP MLD MAC address may be mapped to one or more AP MACaddresses, and mapping information corresponding thereto may be includedin the address table. One STA MLD MAC address may be mapped to one ormore STA MAC addresses, and mapping information corresponding theretomay be included in the address table. The AP MLD may identify addressinformation based on the address table. For example, when the STA MLDMAC address is received, the AP MLD may identify one or more STA MACaddresses mapped to the STA MLD MAC address based on the address table.

In addition, the STA MLD may manage and/or update the address table. Theaddress table may include ‘mapping information between the AP MLD MACaddress and the AP MAC address(es)’ and/or ‘mapping information betweenthe STA MLD MAC address and the STA MAC address(es)’. The AP MLD mayreceive a packet from the network, identify the address of the STA MLDincluded in the packet, identify link(s) supported by the STA MLD, andidentify STA(s) in charge of the link(s) from the address table. The APMLD may configure the STA MAC address(es) of the identified STA(s) asreceiver address(es) and may generate and transmit frame(s) includingthe receiver address(es).

Meanwhile, in a wireless LAN system, a negotiation procedure for amulti-link operation (e.g., multi-link negotiation procedure) may beperformed in an access procedure between a STA and an AP.

A device (e.g., AP or STA) supporting a multi-link may be referred to asa multi-link device (MLD). An AP supporting a multi-link may be referredto as an AP MLD, and a STA supporting a multi-link may be referred to asa non-AP MLD or STA MLD. The AP MLD may have a physical address (e.g.,MAC address) for each link. The AP MLD may be implemented as if an AP incharge of each link exists separately. A plurality of APs may be managedwithin one AP MLD. Accordingly, coordination between the plurality ofAPs belonging to the same AP MLD may be possible. The STA MLD may have aphysical address (e.g., MAC address) for each link. The STA MLD may beimplemented as if an STA in charge of each link exists separately. Aplurality of STAs may be managed within one STA MLD. Accordingly,coordination between the plurality of STAs belonging to the same STA MLDmay be possible.

For example, an AP1 of the AP MLD and a STA1 of the STA MLD may each bein charge of a first link and may communicate using the first link. AnAP2 of the AP MLD and a STA2 of the STA MLD may each be in charge of asecond link and may communicate using the second link. The STA2 mayreceive state change information for the first link in the second link.In this case, the STA MLD may collect information (e.g., state changeinformation) received from each link and may control operationsperformed by the STA1 based on the collected information.

FIG. 3 is a sequence chart illustrating a first embodiment of anegotiation procedure for a multi-link operation in a wireless LANsystem.

As shown in FIG. 3 an access procedure between an STA and an AP in aninfrastructure basic service set (BSS) may generally be divided into aprobe step of probing AP(s), an authentication step for authenticationbetween the STA and the probed AP, and an association step ofassociation between the STA and the authenticated AP.

In the probe step, the STA may detect one or more APs using a passivescanning scheme or an active scanning scheme. When the passive scanningscheme is used, the STA may detect one or more APs by overhearingbeacons transmitted by the one or more APs. When the active scanningscheme is used, the STA may transmit a probe request frame and maydetect one or more APs by receiving probe response frames that areresponses to the probe request frame from the one or more APs.

When the one or more APs are detected, the STA may perform anauthentication step with the detected AP(s). In this case, the STA mayperform the authentication step with a plurality of APs. Anauthentication algorithm according to the IEEE 802.11 standard may beclassified into an open system algorithm of exchanging twoauthentication frames, a shared key algorithm of exchanging fourauthentication frames, and the like.

The STA may transmit an authentication request frame based on theauthentication algorithm according to the IEEE 802.11 standard and maycomplete authentication with the AP by receiving an authenticationresponse frame that is a response to the authentication request framefrom the AP.

When the authentication with the AP is completed, the STA may perform anassociation step with the AP. In particular, the STA may select one APamong AP(s) with which the STA has performed the authentication step,and the STA may perform the association step with the selected AP. Inother words, the STA may transmit an association request frame to theselected AP and may complete the association with the AP by receiving anassociation response frame that is a response to the association requestframe from the selected AP.

Meanwhile, a multi-link operation may be supported in the wireless LANsystem. A multi-link device (MLD) may include one or more STAsaffiliated with the MLD. The MLD may be a logical entity. The MLD may beclassified into an AP MLD and a non-AP MLD. Each STA affiliated with theAP MLD may be an AP, and each STA affiliated with the non-AP MLD may bea non-AP STA. In order to configure a multi-link, a multi-link discoveryprocedure, a multi-link setup procedure, and the like may be performed.The multi-link discovery procedure may be performed in the probe stepbetween an STA and an AP. In this case, multi-link information elements(ML IEs) may be included in the beacon frame, the probe request frame,and/or the probe response frame.

For example, in order to perform a multi-link operation, in the probestep, the AP (e.g., AP affiliated with an MLD) may exchange informationindicating whether the multi-link operation can be used and informationon available link(s) with the STA (e.g., non-AP STA affiliated with anMLD). In a negotiation procedure for the multi-link operation (e.g.,multi-link setup procedure), the STA may transmit information of link(s)to be used for the multi-link operation. The negotiation procedure forthe multi-link operation may be performed in the access procedure (e.g.,association step) between the STA and the AP, and information element(s)required for the multi-link operation may be configured or changed by anaction frame in the negotiation procedure.

In addition, in the access procedure (e.g., association step) betweenthe STA and the AP, available link(s) of the AP may be configured, andan identifier (ID) may be assigned to each link. Thereafter, in thenegotiation procedure and/or change procedure for the multi-linkoperation, information indicating whether each link is activated may betransmitted, and the information may be expressed using the link ID(s).

The information indicating whether the multi-link operation can be usedmay be transmitted and received in a procedure of exchanging capabilityinformation element(s) (e.g., EHT capability information element(s))between the STA and the AP. The capability information element(s) mayinclude information of supporting band(s), information of supportinglink(s) (e.g., ID(s) and/or number of supporting link(s)), informationof links capable of simultaneous transmission and reception (STR)operations (e.g., information on bands of the links, information on aseparation between the links), and/or the like. In addition, thecapability information element(s) may include information thatindividually indicates a link capable of the STR operation.

FIG. 4 is a sequence chart illustrating a first embodiment of a methodfor transmitting and receiving data according to an address resolutionprotocol (ARP) operation in a wireless LAN system.

As shown in FIG. 4 , communication (e.g., Internet protocol (IP)communication) using a multi-link may be performed between an AP MLD,which is a first MLD, and a non-AP MLD (e.g., STA MLD), which is asecond MLD. In order to perform the IP communication, an IP address ofthe AP MLD and an IP address of the STA MLD may be configured. Each ofthe AP MLD and STA MLD may support two links (e.g., a first link and asecond link). An AP1 included in the AP MLD may be in charge of thefirst link, and an AP2 included in the AP MLD may be in charge of thesecond link. A STA1 included in the STA MLD may be in charge of thefirst link, and a STA2 included in the STA MLD may be in charge of thesecond link. When an association procedure between the AP MLD and theSTA MLD is completed (e.g., when the AP MLD and the STA MLD is in acommunicable state), the AP MLD and/or STA MLD may use one link of themulti-link to acquire the IP address required for the IP communication(S401). The operation of acquiring the IP address may be performed usinga dynamic host configuration protocol (DHCP). Performing a DHCPprocedure by using the first link may mean that the STA1 performs theDHCP procedure through the AP1.

In the DHCP procedure, the STA1 may transmit a DHCP discovery message(e.g., DHCP discovery packet) to a DHCP server (e.g., communicationnode) located in the network. Address fields included in a MAC frameheader of the DHCP discovery message may be set to [Transmitter address:MAC address of STA1, Receiver address: FF:FF:FF:FF:FF:FF]. The MACaddress of the STA1 may be a STA MAC address. The transmitter addressmay be a source address, and the receiver address may be a destinationaddress. ‘FF:FF:FF:FF:FF:FF’ may be a broadcast address. Address fieldsincluded in a DHCP IP packet may be set to [Source IP: 0.0.0.0,Destination IP: 255.255.255.255, Client address: MAC address of STAMLD]. The MAC address of the STA MLD may be the STA MLD MAC address.‘255.255.255.255’ may be a broadcast address. Alternatively, the clientaddress may be set to the MAC address of the STA1 (e.g., the MAC addressof the STA1 supporting the first link on which the DHCP procedure isperformed).

The DHCP server may receive the DHCP discovery message, generate a DHCPoffer message (e.g., DHCP offer packet) based on the DHCP discoverymessage, and transmit the DHCP offer message to the STA1 through theAP1. The AP1 may receive the DHCP offer message from the DHCP server andtransmit the DHCP offer message to the STA1. Address fields included ina MAC frame header of the DHCP offer message may be set to [Transmitteraddress: MAC address of AP1, Receiver address: FF:FF:FF:FF:FF:FF].Address fields included in a DHCP IP packet may be set to [Source IP: IPaddress of DHCP server, Destination IP: 255.255.255.255]. Address fieldsof a DHCP payload may be set to [Your IP address: assigned IP address,Client MAC address: MAC address of STA MLD or MAC address of STA1]. Theclient MAC address may be set to the MAC address of the STA1 in chargeof the first link on which the DHCP procedure is performed. The DHCPpayload may include a subnet parameter, router IP address, domain namesystem (DNS) server IP address, IP lease time, and/or DHCP server ID.

The STA1 may receive the DHCP offer message, generate a DHCP requestmessage based on the DHCP offer message, and transmit the DHCP requestmessage to the DHCP server. Address fields included in a MAC frameheader of the DHCP request message may be set to [Transmitter address:MAC address of STA1, Receiver address: FF:FF:FF:FF:FF:FF]. Addressfields of a DHCP IP packet may be set to [Source IP: 0.0.0.0,Destination IP: 255.255.255.255]. Address fields of a DHCP payload maybe set to [Requested IP address: requested IP address, Client MACaddress: MAC address of STA MLD1 or MAC address of STA1]. The requestedIP address may be set to one IP address selected from IP addressesincluded in the DHCP offer message. The client MAC address may be theMAC address of the STA1 supporting the first link on which the DHCPprocedure is performed. The DHCP payload may further include the DHCPserver ID.

The DHCP server may receive the DHCP request message from the STA1 andmay transmit a DHCP ACK message for the DHCP request message to the STA1through the AP1. The AP1 may receive the DHCP ACK message from the DHCPserver and transmit the DHCP ACK message to the STA1. Address fieldsincluded in a MAC frame header of the DHCP ACK message transmitted bythe AP1 may be set to [Transmitter address: MAC address of the AP1,Receiver address: FF:FF:FF:FF:FF:FF]. Address fields of a DHCP IP packetmay be set to [source IP: IP address of the DHCP server, destination IP:255.255.255.255]. Address fields of a DHCP payload may be set to [YourIP: assigned IP address, Client MAC address: MAC address of STA MLD orMAC address of STA1]. The client MAC address may be the MAC address ofthe STA in charge of the first link on which the DHCP procedure isperformed. The DHCP payload may further include a subnet parameter,router IP address, DNS server IP address, IP lease time, and/or DHCPserver ID.

The STA1 may receive the DHCP ACK message. The STA1 may performcommunication using the IP address (e.g., determined IP address) duringthe IP lease time indicated by the DHCP ACK message. The AP1 may operatein a relay mode or proxy mode. In this case, the AP1 may operateidentically or similarly to the above-described method. The DHCPprocedure may be performed using the first link on which the STA1 andthe AP1 operate. In this case, the client MAC address included in theDHCP payload may be set to the MAC address of the STA MLD or the MACaddress of the STA1. When a message includes the MAC address of the STAMLD, a MAC frame header of the message may include the MAC address ofthe STA1, and a DHCP payload of the IP packet may include the MACaddress of the STA MLD.

When the IP configuration procedure is completed, the communication node(e.g., the STA MLD or the STA1) may perform IP communication using theIP address. In order for the network (e.g., router) to forward a packetto the IP address of the STA1 (or the IP address of the STA MLD), anaddress resolution protocol (ARP) procedure, which is a mappingprocedure between the IP address and the MAC address, may be performed.The communication node (e.g., router) of the network may broadcast anARP request packet to obtain an address (e.g., MAC address) of a layer 2entity mapped to a destination IP address of the IP packet (S402). TheARP request packet may include the destination IP address (e.g., the IPaddress of the STA MLD). The AP MLD (e.g., AP1 and/or AP2) may receivethe ARP request packet from the communication node and broadcast the ARPrequest packet to acquire the MAC address of the STA MLD (or STA1 and/orSTA2) having the IP address indicated by the ARP request packet (S403).In the communication system supporting a multi-link, the ARP operationmay be performed according to various methods.

[ARP Operation Performing Method 1]

In the ARP operation performing method 1, an ARP operation may beperformed independently for each link. For example, an ARP operationbetween the AP1 and the STA1 may be performed on the first link, and anARP operation between the AP2 and the STA2 may be performed on thesecond link. The AP MLD may control APs (e.g., AP1 and/or AP2) in chargeof the respective links to broadcast an ARP request packet (S403). Inother words, the AP1 may broadcast the ARP request packet on the firstlink, and the AP2 may broadcast the ARP request packet on the secondlink. The STA1 may receive the ARP request packet from the AP1 on thefirst link and may transmit an ARP response packet as a response to theARP request packet to the AP1 through the first link (S404). The AP1 mayreceive the ARP response packet from the STA1 on the first link. TheSTA2 may receive the ARP request packet from the AP2 on the second linkand may transmit an ARP response packet as a response to the ARP requestpacket to the AP2 through the second link (S404). The AP2 may receivethe ARP response packet from the STA2 on the second link.

FIG. 5A is a block diagram illustrating a first embodiment of a formatof an ARP packet.

As shown in FIG. 5A, an ARP request packet and an ARP response packetmay have the same format (e.g., format according to IPv4). If a value ofan operation field included in a payload of an ARP packet is 1, the ARPpacket may be an ARP request packet. If the value of the operation fieldincluded in the payload of the ARP packet is 2, the ARP packet may be anARP response packet. Since each AP included in the AP MLD transmits theARP request packet on each link, a sender hardware address included in apayload of the ARP request packet may be set to a 48-bit MAC address ofthe corresponding AP. Since each AP does not know a target hardwareaddress, a target hardware address included in the payload of the ARPrequest packet may be set to ‘FF:FF:FF:FF:FF:FF’ (e.g., broadcastaddress).

A sender hardware address included in a payload of the ARP responsepacket may be set to a 48-bit MAC address of the corresponding STA. Atarget hardware address included in the payload of the ARP responsepacket may be set to the 48-bit MAC address of the AP which is areceiving target. Alternatively, the AP MLD MAC address instead of theAP MAC address may be included in the payload of the above-described ARPrequest or response packet, and the STA MLD MAC address instead of theSTA MAC address may be included in the payload of the above-describedARP request or response packet.

Referring again to FIG. 4 , when the AP MLD MAC address and/or the STAMLD MAC address are used, the STAs receiving the ARP request packet maytransmit the corresponding ARP request packet to the STA MLD. Aredundancy check may be performed on the ARP request packets, and thenthe corresponding ARP request packet may be transmitted to an entitycapable of processing the ARP request packet (e.g., an entity includedin the STA MLD). The aforementioned entity may process the ARP requestpacket, generate an ARP response packet, and transmit the generated ARPresponse packet to the STAs (e.g., STA1 and/or STA2). The STAs maytransmit the ARP response packets to the APs (e.g., AP1 and/or AP2). TheAPs may receive the ARP response packets from the STAs and transmit theARP response packets to the AP MLD. A redundancy check may be performedon the ARP response packets, and the AP MLD may transmit one ARPresponse packet to the network (e.g., communication node located in thenetwork) (S405).

The STA MLD may control the ARP response packet to be transmittedthrough one link (e.g., one STA). In this case, since one ARP responsepacket is received, the AP MLD may not perform a redundancy check on theARP response packet. In other words, the AP MLD may transmit the ARPresponse packet to the communication node without performing redundancycheck. The communication node may receive the ARP response packet fromthe AP MLD and may identify the STA MLD MAC address and/or the STA MACaddress included in the ARP response packet. The communication node maytransmit data using the STA MLD MAC address and/or the STA MAC address(S406).

FIG. 5B is a block diagram illustrating a first embodiment of anEthernet frame.

As shown in FIG. 5B, an Ethernet frame may include data, and a MACdestination field included in a MAC header of the Ethernet frame may beset to the STA MLD MAC address and/or the STA MAC address.

[ARP Operation Performing Method 2]

In the ARP operation performing method 2, the AP MLD may transmit an ARPrequest packet using some links (e.g., link(s) receivable by all STAMLDs or all STAs) among multiple links, and STA(s) receiving the ARPrequest packet may transmit an ARP response packet in response to theARP request packet. Here, some APs among the APs included in the AP MLDmay transmit the ARP request packets using some links. The AP MLD mayselect some links receivable by all STA MLDs or all STAs from among themultiple links.

For example, there may be a first link, a second link, and a third link,a STA MLD1 may use the first link and the second link, a STA MLD2 mayuse the second link and the third link, and a STA MLD3 may use the firstlink and the third link. When the AP MLD transmits the ARP requestpacket using the first link, only the STA MLD1 and the STA MLD3 mayreceive the ARP request packet. When the AP MLD transmits the ARPrequest packet using the second link, only the STA MLD1 and the STA MLD2may receive the ARP request packet. When the AP MLD transmits the ARPrequest packet using the third link, only the STA MLD2 and the STA MLD3may receive the ARP request packet. Accordingly, the AP MLD may transmitthe ARP request packet using the first link and second link or using thesecond link and the third link, so that all the STA MLDs receive the ARPrequest packet.

The STA MLD may receive the ARP request packet from the AP MLD and maytransmit an ARP response packet to the AP MLD in response to the ARPrequest packet. Even when the ARP request packet is received through aplurality of links, the STA MLD may transmit the ARP response packet tothe AP MLD using at least one link among the plurality of links. Asender/target hardware address of the ARP request/response packet may beset to the MLD MAC address (e.g., AP MLD MAC address, STA MLD MACaddress).

FIG. 6 is a sequence chart illustrating a second embodiment of a methodfor transmitting and receiving data according to an ARP operation in awireless LAN system.

As shown in FIG. 6 , each of the AP MLD and STA MLD may support twolinks (e.g., a first link and a second link). The AP1 included in the APMLD may be in charge of the first link, and the AP2 included in the APMLD may be in charge of the second link. The STA1 included in the STAMLD may be in charge of the first link, and the STA2 included in the STAMLD may be in charge of the second link. The STA MLD may perform an IPaddress configuration operation (e.g., DHCP procedure) with a DHCPserver (e.g., communication node) via the AP MLD (S601). The IP addressconfiguration procedure may be performed using one link among themultiple links (e.g., the first link and the second link). The AP MLDmay perform a role of a DHCP server, DHCP proxy, or DHCP relay.

The AP MLD may generate and/or store an ARP table (e.g., address table)including IP addresses (e.g., Your IP address) and MAC addresses (e.g.,client MAC address) (S602). The IP addresses and/or MAC addresses may beidentified in the DHCP procedure (e.g., step S601). Information on amapping relationship between the IP addresses and the MAC addresses maybe included in the ARP table. The MAC addresses in the ARP table mayinclude the STA MLD MAC addresses and the STA MAC addresses. In the ARPtable, the STA MAC address(es) may depend on the STA MLD MAC address.For example, the MAC address of the STA MLD may be mapped with the MACaddress(es) of the STA(s) affiliated with the STA MLD. The ARP tablegenerated by the AP MLD may be as shown in Table 1 below.

TABLE 1 ARP table IP address MAC address Entity 111.111.111.111 22-20STA MLD 111.111.111.111 22-21 STA1 111.111.111.111 22-22 STA2

The AP MLD may identify the STA MLD using the ARP table. When the clientMAC address included in the DHCP message is the STA MLD MAC address, theAP MLD may identify the STA MLD based on the STA MLD MAC address. Whenthe client MAC address included in the DHCP message is the STA MACaddress, the AP MLD may identify the STA MLD mapped to the STA MACaddress and may generate the ARP table (e.g., binding table or addresstable) including information on the mapping relationship of ‘IPaddress-STA MLD MAC address-STA MAC address’.

Referring to the ARP table defined in Table 1, the MAC address of theSTA MLD may be 22-20, the MAC address of the STA1 affiliated with theSTA MLD may be 22-21, and the MAC address of the STA2 affiliated withthe STA MLD may be 22-22. The MAC address of the STA1 and the MACaddress of the STA2 may depend on the MAC address of the STA MLD. TheSTA MLD and the STA(s) affiliated with the STA MLD may have the same IPaddress (i.e., 111.111.111.111). The same IP address may be mapped tothe MAC address of the STA MLD, the MAC address of the STA1, and the MACaddress of the STA2.

Meanwhile, the communication node may transmit, to the AP MLD, an ARPrequest packet requesting a layer 2 address (e.g., MAC address) mappedto 111.111.111.111 to perform communication with other communicationnodes (e.g., STA MLD, STA1, and/or STA2) having the IP address set to111.111.111.111 (S603). For example, if there is a data unit to betransmitted to the STA1 and the STA2 included in the STA MLD, thecommunication node may transmit, to the AP MLD, an ARP request packetrequesting the MAC address (e.g., representative MAC address) of the STAMLD with which the STA1 and the STA2 are affiliated. The ARP requestpacket may be transmitted to request the MAC address of the STA MLDinstead of the MAC addresses of the STA1 and the STA2 even when the STAMLD, STA1, and STA2 have different MAC addresses. The ARP request packetmay include an indicator requesting provision of the MAC address (e.g.,representative MAC address) of the STA MLD among the STA MLD, STA1, andSTA2 having the same IP address.

The AP MLD may receive the ARP request packet from the communicationnode and may identify that transmission of the MAC address mapped to111.111.111.111 is requested based on information included in the ARPrequest packet. In this case, the AP MLD may identify the MAC addresses(e.g., 22-20, 22-21, and 22-22) mapped to 111.111.111.111 from the ARPtable. The AP MLD may generate an ARP response packet including at leastone of the MAC address of the STA MLD, the MAC address of the STA1, orthe MAC address of the STA2 on behalf of the STA MLD. The AP MLD maytransmit the ARP response packet to the communication node (S604). TheARP response packet may include a MAC address of a representativecommunication node (e.g., a representative MAC address of thecommunication node) among the communication nodes (e.g., STA MLD, STA1,and STA2) having the same IP address. The representative communicationnode may be the MLD (i.e., STA MLD). The AP MLD may not transmit the ARPrequest packet received from the communication node to the STA MLD andmay generate and transmit an ARP response packet to the communicationnode on behalf of the STA MLD. In the case that the ARP response packetis transmitted by the AP MLD on behalf of the STA MLD, the AP MLD maynot need to broadcast the ARP request packet using all links.Accordingly, radio resources can be saved. The procedure for the AP MLDto transmit the ARP response packet on behalf of the STA MLD may bereferred to as a proxy ARP procedure.

Meanwhile, the communication node may receive the ARP response packetfrom the AP MLD and may identify at least one of the MAC address of theSTA MLD, the MAC address of the STA1, or the MAC address of the STA2included in the ARP response packet. The ARP response packet may includethe MAC address of the representative communication node (e.g., STA MLD)among the communication nodes (e.g., STA MLD, STA1, and STA2) having thesame IP address (e.g., 111.111.111.111). The communication node maytransmit data for the STA MLD using the identified address (S605). Forexample, when data (e.g., IP packet) to be transmitted to the STA MLD(e.g., the STA MLD having the IP address of 111.111.111.111) exists inthe communication node, the communication node may generate a data frame(e.g., Ethernet frame) included the data. The data (e.g., IP packet) maybe included in a payload of the data frame. A receiver address of thedata frame may be set to the STA MLD MAC address. The data frame mayinclude a traffic identifier (TID) for the data. The TID may bedetermined according to the type of the data.

The AP MLD may receive the data frame from the communication node. TheAP MLD may identify a receiver address (e.g., STA MLD MAC address)and/or the type of the data based on information included in the dataframe. The AP MLD may identify link(s) mapped to the TID based on‘TID-link mapping information’ (S606). For example, the AP MLD mayidentify the TID for the data included in the data frame, identifylink(s) associated with the TID (e.g., link(s) on which the data is tobe transmitted) based on the TID-link mapping information, and determinecommunication node(s) (e.g., STA1 and STA2) operating on the link(s) asfinal destination(s). Even when the MAC address of the final destinationof the corresponding data is not included in the data frame receivedfrom the communication node, the AP MLD may identify the finaldestination to which the data is to be transmitted based on the TID-linkmapping information. When the final destinations are the STA1 and theSTA2, the AP MLD may generate a data unit to be transmitted to the STA1and the STA2. Here, the TID for the data frame may be mapped to thefirst link and the second link. Accordingly, the AP MLD may transmit thedata to the STA MLD using both the first link and the second link.

To use both the first link and the second link, the AP MLD may generatetwo MAC protocol data units (MPDUs) based on the data received from thecommunication node (S607). A receiver address of the first MPDU of thetwo MPDUs may be set to the MAC address of the STA1 (e.g., 22-21), and areceiver address of the second MPDU of the two MPDUs may be set to theMAC address of the STA2 (e.g., 22-22). The data of the STA MLD receivedfrom the communication node may be mapped to the STA1 and the STA2. Thefirst MPDU and the second MPDU may include the same data. Alternatively,the first MPDU and the second MPDU may include different data.

The AP MLD may deliver the same data to the AP1 and the AP2.Alternatively, the AP MLD may divide the data received from thecommunication node into two data units (e.g., a first data unit and asecond data unit). For example, a payload of the Ethernet frame receivedfrom the communication node may be divided into the first data unit andthe second data unit. The AP MLD may transmit a first Ethernet frameincluding the first data unit to the AP1 and may transmit a secondEthernet frame including the second data unit to the AP2. A MAC headerof each of the first Ethernet frame and the second Ethernet frame may beconfigured identically to a MAC header of the Ethernet frame receivedfrom the communication node. A receiver address of the first Ethernetframe received by the AP1 from the AP MLD may be the STA MLD MACaddress, and a receiver address of the second Ethernet frame received bythe AP2 from the AP MLD may be the STA MLD MAC address. In other words,the receiver address of the first Ethernet frame may be the same as thereceiver address of the second Ethernet frame. The AP1 may generate thefirst MPDU having, as a receiver address, the MAC address of the STA1mapped to the STA MLD MAC address, which is the receiver address of thefirst Ethernet frame received from the AP MLD. The AP1 may transmit afirst PPDU including the first MPDU using the first link. The AP2 maygenerate a second MPDU having, as a receiver address, the MAC address ofthe STA2 mapped to the STA MLD MAC address, which is the receiveraddress of the second Ethernet frame received from the AP MLD. The AP2may transmit a second PPDU including the second MPDU using the secondlink. When delivering the data (e.g., the first data unit) to the AP1,the AP MLD may change the receiver address from the STA MLD MAC addressto the MAC address of the STA1 operating on the first link. Whendelivering the data (e.g., the second data unit) to the AP2, the AP MLDmay change the receiver address from the STA MLD MAC address to the MACaddress of the STA2 operating on the second link. The AP1 may generatethe first MPDU by using information included in the MAC header of theEthernet frame (e.g., the first Ethernet frame) received from the AP MLDas it is. The AP2 may generate the second MPDU by using informationincluded in the MAC header of the Ethernet frame (e.g., the secondEthernet frame) received from the AP MLD as it is.

The TID of the data received from the communication node may be mappedto one link (e.g., the first link). The AP MLD may identify the TID ofthe data received from the communication node and may deliver thecorresponding data to the AP1 to deliver the data to the first linkmapped to the identified TID. The AP1 may receive the data from the APMLD, generate a first MPDU including the data, and transmit thegenerated first MPDU to the STA1. A receiver address of the first MPDUmay be set to the MAC address of the STA1.

When the size of the data received from the communication node is S andthe number of links available for transmission of the data is L, thesize of data included in a data unit (e.g., MPDU, physical layerconvergence protocol (PLCP) protocol data unit (PPDU)) transmitted oneach link may be S/L. In other words, the size of the data transmittedon each link may be the same. Alternatively, the size of datatransmitted on each link may be determined according to an occupancystate (e.g., occupancy rate) of the corresponding link. For example, thesize of data transmitted on a link having a high occupancy rate may besmaller than that of data transmitted on a link having a low occupancyrate.

The AP1 of the AP MLD may transmit the first PPDU including the firstMPDU to the STA1 using the first link (S608). A transmitter address ofthe first PPDU may be set to the MAC address of the AP1 (e.g., 11-11),and a receiver address of the first PPDU may be set to the MAC addressof the STA1 (e.g., 22-21). The STA1 of the STA MLD may receive the firstPPDU from the AP1 on the first link. The AP2 of the AP MLD may transmitthe second PPDU including the second MPDU to the STA2 using the secondlink (S609). A transmitter address of the second PPDU may be set to theMAC address of the AP2 (e.g., 11-12), and a receiver address of thesecond PPDU may be set to the MAC address of the STA2 (e.g., 22-22). TheSTA2 of the STA MLD may receive the second PPDU from the AP2 on thesecond link.

The first MPDU may be delivered from the STA1 to the STA MLD, and thesecond MPDU may be delivered from the STA2 to the STA MLD. The STA MLDmay restore an IP packet by assembling the data included in the firstMPDU and the data included in the second MPDU (S610). An IP address ofthe IP packet may be the IP address of the STA MLD.

FIGS. 7A and 7B are sequence charts illustrating a third embodiment of amethod for transmitting and receiving data according to an ARP operationin a wireless LAN system.

As shown in FIGS. 7A and 7B, the STA MLD may perform a soft AP function.The STA MLD may be associated with a plurality of STAs (e.g., STA1,STA2, STA3, and STA4). In other words, the STA MLD may serve as an AP.Each of the STA MLD and the plurality of STAs may perform an operationof configuring (e.g., acquiring) an IP address with a DHCP server (e.g.,communication node). For example, the STA MLD may perform an IP addressconfiguration operation with the DHCP server (S701). According to stepS701, the IP address of the STA MLD may be set to 111.111.111.111. TheSTA1 may perform an IP address configuration operation with the DHCPserver (S702). According to step S702, the IP address of the STA1 may beset to 111.111.111.112. The STA2 may perform an IP address configurationoperation with the DHCP server (S703). According to step S703, the IPaddress of the STA2 may be set to 111.111.111.113. The STA3 may performan IP address configuration operation with the DHCP server (S704).According to step S704, the IP address of the STA3 may be set to111.111.111.114. The STA4 may perform an IP address configurationoperation with the DHCP server (S705). According to step S705, the IPaddress of the STA4 may be set to 111.111.111.115.

The AP MLD may monitor the IP address configuration operations. Forexample, the AP MLD may identify the IP address of the STA MLD and/orthe IP addresses of the STAs based on information included in messages(e.g., DHCP messages, DHCP packets) transmitted and received in the IPaddress configuration operations. The AP MLD may map the IP addresses toMAC addresses and may generate and/or store an ARP table includinginformation on a mapping relationship between the IP addresses and theMAC addresses (S706). The ARP table (e.g., binding table, address table)may be configured as shown in Table 2 below.

TABLE 2 ARP table IP address MAC address Via Entity 111.111.111.11122-20 22-20 STA MLD 111.111.111.112 22-21 22-20 STA1 111.111.111.11322-22 22-20 STA2 111.111.111.114 22-23 22-20 STA3 111.111.111.115 22-2422-20 STA4

Since the STAs are associated with the soft AP (e.g., STA MLD), Table 2may further include a Via field. In Table 2, the Via field may be set tothe MAC address of the soft AP with which the STAs are associated. Sincethere is no upper entity connected to the STA MLD, the Via field of theSTA MLD may be set to the MAC address of the STA MLD. Similarly, the ARPtable defined in Table 1 may further include a Via field.

Meanwhile, the communication node may transmit an ARP request packetrequesting a layer 2 address (e.g., MAC address) mapped to111.111.111.114 to the AP MLD to perform communication with the STA3having the IP address set to 111.111.111.114 (S707). The AP MLD mayreceive the ARP request packet from the communication node and mayidentify that transmission of the MAC address mapped to 111.111.111.114is requested based on information included in the ARP request packet. Inthis case, the AP MLD may identify, from the ARP table, the MAC address(e.g., 22-23) mapped to 111.111.111.114 and the MAC address (e.g.,22-20) of the soft AP with which the STA3 having the IP address set to111.111.111.114 is associated. The AP MLD may generate an ARP responsepacket including the identified MAC address (e.g., 22-23) of the STA3 onbehalf of the STA3. In other words, the ARP response packet may includethe MAC address of the STA3. Alternatively, the AP MLD may generate anARP response packet including the MAC address (e.g., 22-20) of the softAP with which the identified STA3 is associated on behalf the STA MLD.In other words, the ARP response packet may include the MAC address ofthe STA MLD. The AP MLD may transmit the ARP response packet to thecommunication node (S708). The AP MLD may not transmit the ARP requestpacket received from the communication node to the STA MLD and/or STA(s)and may transmit the ARP response packet to the communication node onbehalf of the STA MLD and/or STA(s).

The communication node may receive the ARP response packet from the APMLD and may identify the MAC address of the STA3 or the MAC address ofthe STA MLD included in the ARP response packet. The communication nodemay transmit data for the STA3 by using the identified MAC address(S709). For example, when data (e.g., IP packet) to be transmitted tothe STA3 (e.g., STA3 having the IP address of 111.111.111.114) exists inthe communication node, the communication node may generate a data frame(e.g., Ethernet frame) including the data. The data (e.g., IP packet)may be included in a payload of the data frame. A receiver address ofthe data frame may be set to the MAC address (e.g., 22-23) of the STA3or the MAC address of the STA MLD.

The AP MLD may receive the data frame from the communication node andidentify that the receiver address of the data frame is the MAC address(e.g., 22-23) of the STA3 or the MAC address (e.g., 22-20) of the STAMLD. The AP MLD may transmit the data to the STA MLD when a receiveraddress of the corresponding data frame is the MAC address (e.g., 22-20)of the STA MLD. The AP MLD may transmit the data to the STA MLD (e.g.,soft AP) by referring to the ARP table in order to transmit the data tothe STA3 when the receiver address of the corresponding data frame isthe MAC address (e.g., 22-23) of the STA3. In this case, the data may betransmitted to the STA3 via the STA MLD. For example, the AP MLD maygenerate an MPDU including the data and may transmit a PPDU generatedbased on the MPDU to the STA MLD (S710). The MPDU transmitted in stepS710 may be configured as shown in FIG. 8 below.

FIG. 8 is a block diagram illustrating a first embodiment of an MPDU.

As shown in FIG. 8 , a frame control field may include a ‘To DS’ fieldand a ‘From DS’ field. In the MPDU transmitted in step S710 of FIG. 7B,the ‘To DS’ field may be set to 1 and the ‘From DS’ field may be setto 1. When the ‘To DS’ field is set to 1 and the ‘From DS’ field is setto 1, address fields of the MPDU (e.g., PPDU) may be set as shown inTable 3 below.

TABLE 3 Address 1 Address 2 Address 3 Address 4 RA TA DA SA

The RA may refer to a receiver address (e.g., receiver address incommunication according to the IEEE 802.11), the TA may refer to atransmitter address (e.g., transmitter address in communicationaccording to the IEEE 802.11), the DA may refer to a final destinationaddress, the SA may refer to an original sender address, and the BSSIDmay refer to an L2 ID of a basic service set (BSS).

Referring again to FIGS. 7A and 7B, if the receiver address of the dataframe is the MAC address (e.g., 22-23) of the STA3 in step S710, thedata may be transmitted to the STA3 via the STA MLD (e.g., soft AP). Inthis case, the Address 1 field of the MPDU may be set to 22-20 (e.g.,the MAC address of the STA MLD), the Address 2 field of the MPDU may beset to 11-10 (e.g., the MAC address of the AP MLD), the Address 3 fieldof the MPDU may be set to 22-23 (e.g., the MAC address of the STA3), andthe Address 4 field of the MPDU may be set to 10-00 (e.g., the MACaddress of the communication node). When multiple links are used, theMAC address of the STA in charge of the link of the soft AP may be setto the Address field 1, and the MAC address of the AP in charge of thecorresponding link may be set to the Address field 2. When the receiveraddress of the data frame is the MAC address (e.g., 22-20) of the STAMLD in step S710, the data may be transmitted to the STA MLD (e.g., softAP). In this case, the Address 3 field of the MPDU may also be set tothe MAC address (e.g., 22-20) of the STA MLD.

The STA MLD may receive the PPDU from the AP MLD, identify the MPDUincluded in the PPDU, and generate an MPDU to be transmitted to the STA3based on the identified MPDU (e.g., Address 3 field). When the receiveraddress of the PPDU received from the AP MLD (e.g., Address 1 field andAddress 3 field) is the STA MLD, the STA MLD may generate an MPDU to bedelivered to the STA3 by referring to a receiver IP address (e.g.,111.111.111.114) included in a payload. The STA MLD may generate a PPDUbased on the generated MPDU and transmit the PPDU to the STA3 (S711).The STA3 may receive the PPDU from the STA MLD, identify the MPDUincluded in the PPDU, and obtain the data from the MPDU. In step S711,the structure of the MAC header of the MPDU may be the same as thestructure of the MAC header transmitted from the AP to the STA. In theMPDU transmitted in step S711, the ‘To DS’ field may be set to 0 and the‘From DS’ field may be set to 1. When the ‘To DS’ field is set to 0 andthe ‘From DS’ field is set to 1, the address fields of the MPDU (e.g.,PPDU) may be set as shown in Table 4 below.

TABLE 4 Address 1 Address 2 Address 3 Address 4 DA BSSID SA N/A

The Address 1 field of the MPDU may be set to 22-23 (e.g., the MACaddress of the STA3), the Address 2 field of the MPDU may be set to22-20 (e.g., the MAC address of the soft AP (e.g., STA MLD)), and theAddress 3 field thereof may be set to 11-10 (e.g., the address of the APMLD).

The embodiments of the present disclosure may be implemented as programinstructions executable by a variety of computers and recorded on acomputer-readable medium. The computer-readable medium may include aprogram instruction, a data file, a data structure, or a combinationthereof. The program instructions recorded on the computer-readablemedium may be designed and configured specifically for the presentdisclosure or can be publicly known and available to those havingordinary skill in the art.

Examples of the computer-readable medium may include a hardware devicesuch as ROM, RAM, and flash memory, which are specifically configured tostore and execute the program instructions. Examples of the programinstructions include machine codes made by, for example, a compiler, aswell as high-level language codes executable by a computer, using aninterpreter. The above hardware device can be configured to operate asat least one software module in order to perform the embodiments of thepresent disclosure, and vice versa.

While the embodiments of the present disclosure and their advantageshave been described in detail, it should be understood that variouschanges, substitutions, and alterations may be made herein withoutdeparting from the scope of the present disclosure.

What is claimed is:
 1. An operation method of a first device in acommunication system, the operation method comprising: receiving, from acommunication node, an address resolution protocol (ARP) request packetrequesting transmission of a medium access control (MAC) address of asecond device associated with the first device; identifying arepresentative MAC address of the second device, which is requested bythe ARP request packet, from an ARP table stored in the first device;and transmitting, to the communication node, an ARP response packetincluding the representative MAC address.
 2. The operation methodaccording to claim 1, wherein the first device is an access point (AP)multi-link device (MLD), wherein the second device is a station (STA)MLD, wherein the STA MLD includes a STA1 and a STA2, wherein a first MACaddress of the STA MLD, a second MAC address of the STA1, and a thirdMAC address of the STA2 are configured independently of each other, andwherein the representative MAC address is the first MAC address.
 3. Theoperation method according to claim 1, wherein the ARP request packetincludes an indicator requesting provision of the representative MACaddress.
 4. The operation method according to claim 1, furthercomprising: receiving a data frame from the communication node; inresponse to that a receiver address of the data frame is set to therepresentative MAC address of the second device, generating a firstphysical layer convergence protocol (PLCP) protocol data unit (PPDU) anda second PPDU based on data included in the data frame; transmitting thefirst PPDU to a STA1 included in the second device; and transmitting thesecond PPDU to a STA2 included in the second device.
 5. The operationmethod according to claim 4, further comprising: determining a trafficidentifier (TID) based on a type of the data; and identifying a firstlink and a second link mapped to the TID among multiple links, whereinthe first PPDU is transmitted to the STA1 through the first link, andthe second PPDU is transmitted to the STA2 through the second link. 6.The operation method according to claim 4, wherein a size of a firstdata unit included in the first PPDU is equal to a size of a second dataunit included in the second PPDU, and the first data unit and the seconddata unit are generated based on the data.
 7. The operation methodaccording to claim 4, wherein the first PPDU includes a first data unitgenerated based on the data, the second PPDU includes a second data unitgenerated based on the data, and a size of the first data unit and asize of the second data unit are determined based on link occupancystates.
 8. The operation method according to claim 1, wherein the ARPrequest packet includes an Internet protocol (IP) address of the seconddevice, the ARP request packet is not transmitted to the second device,and the ARP response packet is transmitted by the first device on behalfof the second device.
 9. The operation method according to claim 1,wherein the ARP table includes an IP address and a MAC address of thesecond device associated with the first device and a MAC address of eachof one or more STAs included in the second device.
 10. The operationmethod according to claim 1, wherein the ARP table is generated based oninformation included in messages transmitted and received in an IPaddress acquisition procedure performed by the second device.
 11. Theoperation method according to claim 1, wherein the first device is an APMLD, the second device is a STA MLD, and the first device is associatedwith the second device through multiple links.
 12. A first device in acommunication system, comprising: a processor; and a memory storing oneor more instructions executable by the processor, wherein the one ormore instructions are executed to perform: receiving, from acommunication node, an address resolution protocol (ARP) request packetrequesting transmission of a medium access control (MAC) address of astation 1 (STA1) included in a second device associated with the firstdevice; identifying a MAC address of the STA1, which is requested by theARP request packet, from an ARP table stored in the first device; andtransmitting, to the communication node, an ARP response packetincluding the MAC address of the STA1.
 13. The first device according toclaim 12, wherein the ARP request packet includes an Internet protocol(IP) address of the STA1, the ARP request packet is not transmitted tothe second device or the STA1, and the ARP response packet istransmitted by the first device on behalf of the second device or theSTA1.
 14. The first device according to claim 12, wherein the seconddevice includes one or more STAs, and an IP address of each of thesecond device and the one or more STAs are configured independently. 15.The first device according to claim 12, wherein the ARP table includesan IP address and a MAC address of the second device associated with thefirst device and an IP address and a MAC address of each of one or moreSTAs included in the second device.
 16. The first device according toclaim 15, wherein the ARP table is generated based on informationincluded in messages transmitted and received in an IP addressacquisition procedure performed by each of the second device and the oneor more STAs.
 17. The first device according to claim 12, wherein theone or more instructions are further executed to perform: receiving adata frame from the communication node; in response to that a receiveraddress of the data frame is set to the MAC address of the STA1 includedin the second device, generating a first physical layer convergenceprotocol (PLCP) protocol data unit (PPDU) based on data included in thedata frame; and transmitting the first PPDU to the second device,wherein an address 1 field included in the first PPDU is set to a MACaddress of the STA MLD, an address 2 field included in the first PPDU isset to a MAC address of the AP MLD, an address field 3 included in thefirst PPDU is set to the MAC address of the STA1, and an address 4 fieldincluded in the first PPDU is set to a MAC address of the communicationnode.